Based on the empirical electronic theory of solids and molecules （EET）, the actual model for unit cell of cementite （0-FeaC） was built and the valence electron structures （VES） of cementite with specified site a...Based on the empirical electronic theory of solids and molecules （EET）, the actual model for unit cell of cementite （0-FeaC） was built and the valence electron structures （VES） of cementite with specified site and a number of Fe atoms substituted by alloying atoms of M （ M=Cr, V, W, Mo, Mn ） were computed by statistical method. By defining P as the stability factor, the stability of alloyed cementite with different numbers and sites of Fe atoms substituted by M was calculated. Calculation results show that the density of lattice electrons, the symmetry of distribution of covalent electron pairs and bond energy have huge influence on the stability of alloyed cementite. It is more stable as M substitutes for FeE than for Fe1. The alloyed cementite is the most stable when Cr, Mo, W and V substitute for 2 atoms of Fe2 at the sites of Nos. 2 and 3 （or No. 6 and No. 7）. The stability of alloyed cementite decreases gradually as being substitutional doped by W, Cr, V, Mo and Mn.展开更多
The influences of nitrogen content and austenitization temperature on Nb（C, N） precipitation in niobium micro-alloyed steels were studied by different methods： optical microscopy, tensile tests, scanning electron m...The influences of nitrogen content and austenitization temperature on Nb（C, N） precipitation in niobium micro-alloyed steels were studied by different methods： optical microscopy, tensile tests, scanning electron mi- croscopy, transmission electron microscopy, physicochemical phase analysis, and small-angle X-ray scattering. The results show that the strength of the steel with high nitrogen content is slightly higher than that of the steel with low nitrogen content. The increase in the nitrogen content does not result in the increase in the amount of Nb（C,N） precipitates, which mainly depends on the niobium content in the steel. The mass fraction of small-sized Nb（C, N） precipitates （1--10 nm） in the steel with high nitrogen content is less than that in the steel with low nitrogen con- tent. After austenitized at 1 150 ℃, a number of large cuboidal and needle-shaped particles are detected in the steel with high nitrogen content, whereas they dissolve after austenitized at 1 200 ℃ and the Nb（C,N） precipitates become finer in both steels. Furthermore, the results also show that part of the nitrogen in steel involves the formation of al- loyed cementite.展开更多
基金Project(2014CFB801)supported by Natural Science Foundation of Hubei Province of ChinaProject(11304236)supported by the National Natural Science Foundation of China
文摘Based on the empirical electronic theory of solids and molecules （EET）, the actual model for unit cell of cementite （0-FeaC） was built and the valence electron structures （VES） of cementite with specified site and a number of Fe atoms substituted by alloying atoms of M （ M=Cr, V, W, Mo, Mn ） were computed by statistical method. By defining P as the stability factor, the stability of alloyed cementite with different numbers and sites of Fe atoms substituted by M was calculated. Calculation results show that the density of lattice electrons, the symmetry of distribution of covalent electron pairs and bond energy have huge influence on the stability of alloyed cementite. It is more stable as M substitutes for FeE than for Fe1. The alloyed cementite is the most stable when Cr, Mo, W and V substitute for 2 atoms of Fe2 at the sites of Nos. 2 and 3 （or No. 6 and No. 7）. The stability of alloyed cementite decreases gradually as being substitutional doped by W, Cr, V, Mo and Mn.
基金Item Sponsored by the CITIC-CBMM Niobium Steel Research and Development Program of China(2013-D065)
文摘The influences of nitrogen content and austenitization temperature on Nb（C, N） precipitation in niobium micro-alloyed steels were studied by different methods： optical microscopy, tensile tests, scanning electron mi- croscopy, transmission electron microscopy, physicochemical phase analysis, and small-angle X-ray scattering. The results show that the strength of the steel with high nitrogen content is slightly higher than that of the steel with low nitrogen content. The increase in the nitrogen content does not result in the increase in the amount of Nb（C,N） precipitates, which mainly depends on the niobium content in the steel. The mass fraction of small-sized Nb（C, N） precipitates （1--10 nm） in the steel with high nitrogen content is less than that in the steel with low nitrogen con- tent. After austenitized at 1 150 ℃, a number of large cuboidal and needle-shaped particles are detected in the steel with high nitrogen content, whereas they dissolve after austenitized at 1 200 ℃ and the Nb（C,N） precipitates become finer in both steels. Furthermore, the results also show that part of the nitrogen in steel involves the formation of al- loyed cementite.
